Repulpable printed paper having water resistant coating



United States Patent 3,287,149 REPULPABLE PRINTED PAPER HAVING WATERRESISTANT COATING Joseph A. Dooley, Belleville, Richard D. Vieth,Kinnelon, and Harry Burrell, North Caldwell, N.J., assignors toInterchemical Corporation, New York, N.Y., a corporation of Ohio NoDrawing. Filed Jan. 22, .1963, Ser. No. 253,039 6 Claims. (Cl. 117-15)The present invention relates to repulpable coated paper and moreparticularly to repulpable coated printed paper stock which hassuflicient gloss and resistance to water or weathering to be used formagazine covers.

Coated paper used for magazine covers must have the followingproperties: (1) it must have very high gloss (2) it must be resistant towater since it is generally exposed to weathering (3) it must curerapidly since in conventional high speed coating operations for magazinecovers, the curing time may be as low as a fraction of a second and (4)finally, and most important, the coated stock must be repulpable, thatis the coating must be readily removable from the paper by theapplication of a dilute, about 2%, aqueous sodium hydroxide solutionwhich is used in commercial deinking processes.

As far as it is known to us, no previous coated paper has achieved thisunique combination of properties without any attendant properties whichare detrimental to the use of the coated paper as a magazine cover. Itis indeed rare to find a coated paper which is highly water resistant sothat it may withstand the efiects of weathering in exposed newsstands,thereby protecting printed matter, and yet may have its coating readilyand completely removable by a dilute alkaline solution.

Among coated papers which have been previously tried for magazinecovers, thermoset alkyd-amine coated papers have been found to bevirtually unrepulpable because the coating can not be separated from thepaper and the inks by a dilute alkaline solution. In additionalkyd-amine coatings do not dry at a sufliciently rapid rate to beutilizable in the high speed printing of magazine covers. On the otherhand, oleoresinous coatings have been too slow in drying when applied inthe film thicknesses required for high gloss in coatings for magazinestock. Furthermore, nitrocellulose lacquer coatings have less thandesirable flammability properties and are too low in gloss for use asmagazine coatings.

We have now found a novel coated paper which has all of the desirablerequired properties set forth above for magazine covers without anyattendant detrimental properties.

The coated paper of this invention comprises a printed magazine stocksubstrate coated with a copolymer comprising the copolymerizationproduct of styrene and the half-ester formed by the half-esterificationof an alphabeta unsaturated dicarboxylic acid such as fumaric or maleicacids with a lower alkanol which has 1 to 8 carbons and preferably 1 to4 carbons, most preferably a n-alkanol such as methanol, n-propanol andn-butano'l as well as n-octanol and 2-ethyl hexanol. That thiscomposition may be removed from the paper by treating with a diluteaqueous sodium hydroxide solution is indeed surprising because compoundscontaining substantial amounts of styrene are conventionally believed tohave at least some alkali resistance.

In the present specification and claims, all proportions are by weightunless otherwise stated.

In preparing the copolymers used in the coating the half-ester is firstformed by esterifying the alkanol with the alpha-beta unsaturated acid,preferably at a temperature in the ragne of from 170 to 300 F., afterwhich the half-ester is polymerized, using a conventional addition "icepolymerization catalyst, with styrene. During the formation of thehalf-ester from about 1.1 to 5.0 moles of alkanol are preferably addedfor each mole of alpha-beta unsaturated acid. During thecopolymerization, preferably about from 0.5 to 2.2 moles and mostpreferably 1 mole of styrene are added for each mole of alpha-beta acidoriginally present. The copolymerization is preferably conducted at atemperature of from 200 to 350 F.

As will be illustrated in the examples, the coatings on the paper ofthis invention may be readily removed during conventional repulping ordeinking in which the paper is treated with about a 2% solution ofsodium hydroxide.

The following examples will illustrate the practice of this invention.

EXAMPLE 1 Copolymer of styrene and butyl-maleic half ester Grams Butanol1836 Maleic anhydride 558 Benzoyl peroxide 30 The above mixture isheated to 210 F. Then 1248 g. of styrene are added slowly over a periodof 1 hour while the mixture is maintained at said temperature. Heatingis continued until a viscosity of about Z on the Gardner- Holdt Scale isachieved.

EXAMPLE 2 copolymer of styrene and methyl-maleic half ester GramsMethanol Maleic anhydride 392 Xylene 624 Benzoyl peroxide 25 The abovemixture is heated to 210 F. Then 460 g. of propanol are added and 832 g.of styrene are added slowly over a period of one hour while the mixtureis maintained at 210 F.

EXAMPLE 3 Copolymer of styrene and propyl-maleic half ester GramsPropanol 1480 Maleic anhydride 558 Benzoyl peroxide 30 The above mixtureis heated to 210 F. Then 1248 g. styrene are added slowly over a periodof one hour while the mixture is maintained at 210 F EXAMPLE 4 Copolymerof styrene and Z-ethyl hexyl-maleic half ester Grams Z-ethyl hexanol2830 Maleic anhydride 558 Benzoyl peroxide 30 The above mixture isheated to 210 F. Then 1248 g. of styrene are added slowly over a periodof one hour while the mixture is maintained at 210 F.

EXAMPLE 5 about 100 square inches of the stock are shredded and placedin a conventional bath for repulping magazine stock comprising 250 ml.of a 2% aqueous sodium hydroxide solution, to which there has been added1 g. of 325 mesh mica as a filtering aid and 3 g. of a wetting agentsuch as the commercial Vel, sodium dodecylbenzene sulfonate, the bathhaving a temperature of 140 F. The mixture is stirred vigorously for 15minutes. The slurry is poured onto a 40 mesh screen and washed with coldtap Water. The mixture is reslurried, stirred for several minutes andagain washed through a screen as described above. The slurry is thenvacuum dried. Careful inspection of the remaining pulp reveals that thecoating has completely disintegrated and been removed.

EXAMPLE 6 66.7 parts of the copolymer of Example 2 are mixed with 16.7parts of xylene and 16.6 parts of propanol and the resulting solution iscoated by gravu're coating onto a magazine cover stock at 6 to 8milligrams per square ,inch and cured in an oven at 275 F. for 10minutes. The coated stock has slightly better block resistance as wellas slightly less gloss than the stock of Example 4. The water resistanceof the stock is excellent. When tested for repulpability in accordancewith the procedure of Example 4, the remaining pulp has substantially nocoating adhering to the printed or unprinted surfaces indicating thatthe coat-ing has been completely disintegrated.

EXAMPLE 7 Example is repeated using the same conditions, proportions andingredients except that 68.9 parts of the copolymer of Example 3 areused. The resulting coated stock has a block resistance slightly betterthan that of Example 5 but not quite as good as that of Example 6 and agloss slightly better than that of Example 6 but not quite as good asthat of Example 5. The water resistance of the stock is excellent.

When tested for repulpability in accordance with the procedure ofExample 5, the remaining pulp has substantially no coating adheringthereto indicating that the coating has been completely disintegrated.

EXAMPLE 8 Example 5 is repeated using the same conditions, proportions,and ingredients except 68.9 parts of the copolymer of Example 4 areused. The resulting coated stock has about the same properties as thestock of Example 5. When tested for repulpability in accordance with theprocedure of Example 5, the remaining pulp has substantially no coatingadhering thereto indicating that the coating has been completelydisintegrated.

It should be noted that the magazine stock described 4 in Examples 5 to8 which is coated may and in commercial practice does contain printedmatter. The magazine stock may be printed upon with any conventional inkused in magazine covers e.g., heat-set inks such as inks having limedand zincated rosin binders and phenolic binders modified with a phenolformaldehyde condensate. All of these conventional inks are readilyremovedduring the repulping process by the action of the dilute alkali.Repulping is also known as deinking.

While :there have been described what is at present considered to be thepreferred embodiments of this invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein.

without departing from the invention, and it is, therefore, aimed tocover all such changes and modifications as fall within the true spiritand scope of the invention.

What is claimed is: 1. A repulpable coated papercomprising a papersubstrate having printing thereon and a water resistant coating over theprinting, said coating consisting essentially of the copolymerizationproduct of styrene and the halfester formed by the half esterificationof 1 mole of an alpha-beta unsaturated dicarboxylic acid selected fromthe group consisting of maleic and fuman'c acids with from 1.1 to 5.0moles of a lower. alkanol, from 0.5 to 2.2

moles of styrene being copolymerized for each mole of said acid.

2. The repulpable coated paper of claim 1 wherein said alkanol has from1 to 4 carbons.

3. The repulpable coated paper of claim 1 wherein said half-ester is themethyl half-ester of maleic .acid.

4. The repulpable coated paper of claim 1 wherein said half-ester is thepropyl half-ester of maleic acid.

5. The repulpable coated paper of claim 1 wherein said half-ester is thebutyl half-ester of maleic acid.

6. The repulpable coated paper of claim 1 wherein said half-ester is the2-ethyl hexyl half-ester of maleic acid.

WILLIAM D. MARTIN, Primary Examiner.

MORRIS O. WOLK, S. L. BASHORE, H. W. MYLIUS.

Assistant Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3, 287,149 November 22 1966 Joseph A. Dooley et a1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 1, line 71, for "ragne" read range column 2, line 8, for "350 F."read 250 F.

Signed and sealed this 12th day of September 1967.

( AL) Attest:

ERNEST W. SWIDER EDWARD]. BRENNER Attesting Officer Commissioner ofPatents

1. A REPULPABLE COATED PAPER COMPRISING A PAPER SUBSTRATE HAVINGPRINTING THEREON AND A WATER RESISTANT COATING OVER THE PRINTING, SAIDCOATING CONSISTING ESSENTIALLY OF THE COPOLYMERIZATION PRODUCT OFSTYRENE AND THE HALFESTER FORMED BY THE HALF ESTERIFICATION OF 1 MOLE OFAN ALPHA-BETA UNSATURATED DICARBOXYLIC ACID SELECTED FROM THE GROUPCONSISTING OF MALEIC AND FUMARIC ACIDS WITH FROM 1.1 TO 5.0 MOLES OF ALOWER ALKANOL, FROM 0.5 TO 2.2 MOLES OF STYRENE BEING COPOLYMERIZED FOREACH MOLE OF SAID ACID.